Random PWM Technique for Dual-Inverter-Fed Vector-Controlled Induction Motor Drive
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Random PWM Technique for Dual-Inverter-Fed Vector-Controlled Induction Motor Drive M. Harsha Vardhan Reddy1 · T. Bramhananda Reddy1 · B. Ravindranath Reddy2 · M. Surya Kalavathi2
Received: 5 September 2014 / Revised: 27 July 2015 / Accepted: 12 September 2015 © Brazilian Society for Automatics–SBA 2015
Abstract From the analysis of harmonic spectrum of conventional PWM techniques, it is observed that a high amount of energy is concentrated around the harmonics of switching frequencies as side bands resulting in acoustic noise, vibration and electromagnetic interference. These effects can be mitigated by spreading the spectrum and reducing the magnitude of harmonics around switching frequencies. This can be achieved by introducing the randomness in control signals. In this paper a simplified and more generalized carrier-based random pulse width modulation (RPWM) technique is presented for asymmetrical dual-inverter-fed vector-controlled induction motor drive. In the proposed RPWM technique a zero sequence signal is added to the commended reference signal to obtain the required modulating signal. The randomness is introduced in generating the zero-sequence signal. To validate the proposed RPWM technique, simulation and experimental studies are carried out and the results are presented. Keywords Asymmetrical dual inverter · Decoupled control · Random PWM
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M. Harsha Vardhan Reddy [email protected] T. Bramhananda Reddy [email protected] B. Ravindranath Reddy [email protected] M. Surya Kalavathi [email protected]
1
Department of EEE, G. Pulla Reddy Engineering College (Autonomous), Kurnool, Andhra Pradesh, India
2
Department of EEE, JNTUH, Kukatpally, Hyderabad, Andhra Pradesh, India
1 Introduction In early 1980s conventional control algorithms are used for separately excited DC motors to have independent (decoupled) control of both torque and flux. Due to which high and fast torque response is achieved. But DC motors require regular maintenance and have high weight to volume ratio. On the other hand, induction motors have low maintenance and low weight volume ratio but has inherent coupling effect. To achieve decoupled control as in DC motor drives, the induction motor stator current vector has to be resolved into two components as flux controlling component and torque controlling component. This scheme is employed in two popular control techniques namely direct torque control and vector control. With the above fast and dynamic control techniques, the DC motor drives are replaced by the induction motor drives especially in applications like hybrid electrical vehicles (HEV), railway locomotives and ship propulsion. When compared to direct torque control vector control technique gives less steady-state ripple. As the main motto of this paper is to reduce steady-state ripple, much focus is given to vector control. Conventional vector control scheme discussed in Blaschke (1972), Leonhard (1991a, b), Dey et al. (2013) uses two-level hysteresis control which gives variable switching fre
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